Climate Dynamics Group
at the University of California, Santa Cruz

• Aaron Donohoe
• Edward Blanchard-Wrigglesworth
• Nicole Feldl

The atmospheric energy budget associated with the heating and cooling of the atmosphere on daily time scales across the globe is analyzed using a fixed atmospheric mass calculation of the instantaneous atmospheric heat flux convergence. The heating and moistening of the atmospheric column during a typical heating event requires of order 1000 W m−2 of energy input to the atmosphere. The required energy input is predominantly provided by the atmospheric heat transport convergence. In contrast, the temporal variability of energy inputs by surface turbulent fluxes and radiation are an order of magnitude smaller. This result suggests that the atmospheric temperature variability is set by the magnitude of variability in lateral energy fluxes in the atmosphere, limited by the heat capacity of the atmosphere, and provides a framework for understanding the controls on heat wave intensity. To relate the magnitude of atmospheric heating to the intensity of heat waves—measured by the variance of surface temperature—additional considerations are made for (i) the temporal duration of heating events, (ii) the fraction of atmospheric energy input that goes into moistening versus warming the atmosphere, and (iii) the vertical structure of temperature changes during heating events. Of these factors, surface heat wave intensity is damped by the moisture storage contribution by a factor of four in the tropics and amplified by the vertical structure of temperature by almost an order of magnitude over extratropical landmasses as compared to the ocean.